To utilize state of the art methodologies derived from clinical, neuroendocrinol ogical and psychoimmunological fields to study a group of patients with chronic fatigue syndrome or neurasthenia. It is hypothesized that a subset of these patients will manifest characteristic immunological abnormalities including T lymphocyte dysfunction, decreased NK cell cytotoxicity, and increased cytokine concentrations. Neuroendocrine changes will include reduced plasma cortisol and ACTH concentrations. Cross ethnic comparability of these findings will also be examined.